This invention relates to hoists used in building concrete walls and in particular to a wall climbing form hoist for handling form units in the construction of concrete wall structures for multi-story buildings.
In the construction of a multi-story building, such as an office building, apartment building and the like, these buildings may have thirty or more floors. Where concrete is used in the construction of the outside walls, it is necessary to provide cranes in the setting up and then stripping of the forms from a set wall panel for reuse in continuing the completion of the wall. Unless a crane is available as required in the setting up and stripping of the forms the wall not only becomes costly, but additional cost increases are incurred by lost time on other operations, that must be performed on a meshing or synchronized time schedule with the wall forming operation. It is apparent also that appreciable down time of the crane may take place, when it could be more efficiently utilized on other jobs at the building site. Where open crane time for timely handling of the form units is not available, construction usually proceeds behind schedule with resultant monetary losses. In some instances, the size of the building being constructed relative to the building site may preclude the use of a crane.
A system for constructing concrete walls about two stories high are shown in U.S. Pat. No. 2,516,318; and for multi-story buildings, in U.S. Pat. Nos. 4,043,087; and 2,118,374. Self-lifting form systems now in use are generally cumbersome and, although inconvenient to manipulate during both a wall climbing operation and a form handling operation, have been found to be generally satisfactory. U.S. Pat. No. 3,628,223 discloses a climbing form hoist that includes a telescopic mast comprised of a pair of vertical lower mast sections for telescopically receiving associated upper mast sections which are extended and retracted by a common reversible electric motor. The upper mast sections carry an outer form unit. With the mast retracted and attached at its lower end to a completed lower wall section, the inner and outer form units are braced or tied together in any well-known manner after which a new lift or wall section is poured. When the new pour has set, the outer form unit, after being stripped from the wall structure, is elevated by the extension of the upper mast sections to a new pour position wherein its lower end is attachable to the previously poured wall section. The lower mast sections are then released from the wall, the upper mast section is retracted and the lower mast section again connected to the wall. The inner form unit is then repositioned for another lift to be poured.